In the case of electric lighting M. Servier has studied two examples--the Jablochkoff candle, and an arc light (system not stated). The former is credited with the illuminating power of 16 Carcels (152 candles), and is fixed at the height of 5 mètres (16 feet 3 inches), on pillars 110 mètres (120 yards) apart. This would give a light of 0·65 Carcel (6·27 candles) at the foot of the pillar, and a minimum intensity of 0·05 Carcel (0·475 candle) midway between the lights. The arc light is purposely made exactly equal in computed efficiency to the larger Siemens burner of 50 Carcels (475 candles). In the matter of expense, however, using the data applicable to Paris, with 12-candle gas at 6_s._ 6_d._ per 1000 cubic feet, M. Servier makes a striking comparison. The cost of lighting a kilomètre of road in the “ordinary” manner last described varies very little for the three classes of gas lamps--small, large, and very powerful--included in the calculation, and ranges from 3·33 frs. to 3·96 frs. per hour. The cost of the same work done by the Jablochkoff candle is estimated at about double, or 6·91 frs. per hour; and with the arc light the cost would be 4 frs., or still higher than with the most costly system of gas lighting, although less than the expense of the Jablochkoff electric light. The following table will show the particulars of different lights so placed that persons may see to read ordinary print in any part of the street, which may be taken as then being a well-lighted street. ----------------------+------------+---------+--------+---------+ | | |Distance| | | | | of |Number of| |Illuminating|Height of| Lamps |Lamps per| Description of Light. | Power. | Lamps. | apart. | Mile. | ----------------------+------------+---------+--------+---------+ _Gas._ | candles. | ft. in. | yards. | | Batswing, 7 cubic feet| 16·34 | 9 10 | 20 | 176 | Cluster, 50 „ „ | 133·00 | 10 6 | 115 | 29 | Siemens, 100 „ „ | 475·00 | 26 3 | 294 | 10 | | | | | | _Electricity_ | | | | | Jablochkoff candle | 152·00 | 16 3 | 120 | 29 | Arc light | 475·00 | 26 3 | 294 | 10 | ----------------------+------------+---------+--------+---------+